Preimplantation embryo genetic testing is a process wherein a sample containing one or several cells is taken using an inverted microscope and micromanipulator and then tested to determine if the respective embryo is chromosomally (genetically) or metabolically normal.
After the sample is taken from an embryo it remains in the drop under oil until it is manually moved into the testing tube with a small amount of solution under control of a dissecting microscope.
This sample transfer represents a considerable challenge to the operator for two reasons. One is that holding a small tube with one hand, while a pipette with a sample in another hand limits operator's ability to focus a dissecting microscope on the sample.
Merely placing a sample onto the edge of a Petri dish solves this problem only partially, because the tube still can wiggle considerably.
Another problem is matching the tube and a sample numbers. Usually there are several samples from several biopsied embryos. It is critical that the sample would be placed into the corresponding tube number. However, the tube is usually too small to place a number on it in such way that it can be readily observed under the microscope without obstructing the view inside of the tube.
As a result, an operator has limited opportunity to verify that the right sample goes into the right tube leading to errors.
In fact, it has been reported that this type of errors is the leading cause of misdiagnosis in preimplantation genetics.